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Even open-label placebos work, if they are explained -- ScienceDaily

For the first time, researchers from the University of Basel, along with colleagues from Harvard Medical School, have compared the effects of administering open-label and deceptive placebos. The team conducted an experimental study with 160 healthy volunteers who were exposed to increasing heat on their forearm via a heating plate. The participants were asked to manually stop the temperature rise as soon as they could no longer stand the heat. After that, they were given a cream to relieve the pain.
Some of the participants were deceived during the experiment: they were told that they were given a pain relief cream with the active ingredient lidocaine, although it was actually a placebo. Other participants received a cream that was clearly labeled as a placebo; they were also given fifteen minutes of explanations about the placebo effect, its occurrence and its effect mechanisms. A third group received an open-label placebo without any further explanation.
The subjects of the first two groups reported a significant decrease in pain intensity and unpleasantness after the experiment. "The previous assumption that placebos only work when they are administered by deception needs to be reconsidered," says Dr. Cosima Locher, a member of the University of Basel's Faculty of Psychology and first author of the study.

Why Do Rich People Love Endurance Sports? | Outside Online

“By flooding the consciousness with gnawing unpleasantness, pain provides a temporary relief from the burdens of self-awareness,” write the researchers. “When leaving marks and wounds, pain helps consumers create the story of a fulfilled life. In a context of decreased physicality, [obstacle course races] play a major role in selling pain to the saturated selves of knowledge workers, who use pain as a way to simultaneously escape reflexivity and craft their life narrative.”

Bring On the Exercise, Hold the Painkillers - The New York Times

It found that by reducing the production of prostaglandins, NSAIDs change how a body responds to exertion, this time deep within the muscles.
For that study, researchers in the department of microbiology at Stanford University looked first at muscle cells and tissue from mice that had experienced slight muscular injuries, comparable to those we might develop during strenuous exercise. The tissue soon filled with a particular type of prostaglandin that turned out to have an important role: It stimulated stem cells within the muscles to start multiplying, creating new muscle cells that then repaired the tissue damage. Afterward, tests showed that the healed muscle tissue was stronger than it had been before.

Power of shared pain triggers extreme self-sacrifice -- ScienceDaily

There were five hypotheses: shared experience promotes willingness to perform extreme pro-group action; shared negative experiences make individuals contribute more than euphoric experiences; the more intense the experience the stronger the pro-social effects; the effect of shared negative experiences on pro-social behavior is much stronger where groups compete directly against other groups rather than if they cooperate against nature; and the effects of shared negative experience can be stronger than those of kinship.
The hypotheses were then tested empirically in a variety of different study populations, including U.S. military veterans of the Vietnam war, college fraternity and sorority members who had undergone hazing, English Premier League football fans, martial arts practitioners of Brazilian Jiu Jitsu who sometimes use painful belt-whipping, and twins to examine the level of fusion.
From both the theoretical and empirical research, the study concluded that overall shared negative experiences are a powerful mechanism for promoting pro-social behaviors, which under certain conditions can be extremely costly to the individuals concerned.

"We were able to show that opioid agonists activate opioid receptors on immune cells, which triggered the release of endogenous painkillers (opioid peptides) and produced analgesia in a mouse model of neuropathic pain," explains Prof. Machelska. She adds, "This led us to conclude that opioids can exert enhanced analgesia when they act directly in painful tissue -- providing that this tissue is inflamed and contain immune cells."

Animal awareness of others' needs

As long ago as 1959, Russell Church of Brown University set up a test which allowed laboratory rats in half of a cage to get food by pressing a lever. The lever also delivered an electric shock to rats in the other half of the cage. When the first group realised that, they stopped pressing the lever, depriving themselves of food. In a similar test on rhesus monkeys reported in the American Journal of Psychiatry in 1964, one monkey stopped giving the signal for food for 12 days after witnessing another receive a shock. There are other examples of animals preferring some sort of feeling over food.